Method and means of boiler control



July 4, 1933 w. J. HUGHES ET AL 1,916,426

METHOD AND MEANS OF BOILER CONTROL Filed May 2, 1927 2 Sheets$heet 1 mgaz July 4, 1933.

w'. J. HUGHES ET AL METHOD AND MEANS OF BOILER CONTROL Filed May 2, 1927 2 Sheets-Sheet 2 [we/W525: WZZZIzr J Hag/1 65, WZLZZerH 6119672, WW yaw/264M Patented July 4, 1933 UNITED STATES PATENT orrlcr.

W'AL'JI'ERv J. HUGHES AND WALTER H. GREEN, OF CHICAGO, ILLINOIS, ASSIGNOBS TO GENERAL ZEOLITE COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS METHOD AND MEANS or BoILERooNrRoL Application filed May 2, 1927. Serial No. 188,103.

This invention relates to a method and means for regulating the quality of the steam generated and controlling the condition of the boiler water.

Boiler feed wateror more particularly the make-up feed water contains mineral substances in solution. The evaporation of such feed water in boilers results in the accumulation of, or in other words, the concentration of, these mineral substances in the water contained in the boiler. Since the amount of water contained by the boiler is kept fairly constant, the process of steaming comprises feeding water to the boiler continuously in such quantities as will replace that which is changed to vapor and leaves the boiler as steam. As'the steaming process is carried on, therefore, the mineral and other impurities of the feed water concentrate in the water remaining in the boiler. Since the amount and kind of impurities concentrated in the boiler water have an effect upon the turbulence with which the water boils, it is known that as the'concentration increases the steam liberated tends to entrain greater quantities of finely divided boiler water. The more unevaporated boiler water there is mingled with the steam, the poorer is its quality and for power purposes, the lower its efliciency. A

It is known that higher steaming rates are accompanied by greater turbulence of the water in the boiler regardless of the presence of impurities. The turbulence is the least with pure water and becomes worse with impure water'usually reaching severe violence as the concentration of impurities becomes too great for the particular operating conditions. v

In order to prevent boiler conditions that cause the generation of steam of low quality, or even priming during which slugs of water may be carried out of the boiler with the steam, it is common practice to reduce the boiler, water concentration at intervals. The usual practice is to draw ofl' a quantity of water from the boiler and replace this with fresh feed water. This operation is spoken of as blow-down ofthe boiler and is usually done by hand once each shift or as frequently as may be necessary to reduce turbulence rated, the rate of evaporation, or the quality of the steam produced. In those instances where the boiler blowdown is regulated in accordance with the amount of feed water admitted to the boiler, a certain amount of proportioning is obtained, but this type of regulation is less satisfactory than the boiler control constituting our invention.

An object of this invention is to provide a method and a means for blowing down the boiler in accordance with the operating conditions. I

Another object of this invention is to provide a method and a means for regulating the quality of the steam generated under varying conditions.

A further object is to provide a method and a means for controlling the condition of the boiler water.

A still further object is to provide a method and a means whereby the amount of boiler blow-down is reduced to the minimum consistent with securing a satisfactory quality of steam under varying operating conditions.

Boiler blow-down may be regulated by, and made proportionate to, the amount of waterevaporated and the rate of evaporating it. Since the boiler feed and the steam output both indicate the amount and rate of evaporation, it is possible to control the boiler blow-down by either one of these factors.

This method of control is satisfactory when the water fed into the boiler is of substantially constant quality (that is contains an unvarying amount of substances in solution and suspension), and when {there are no great variations in the load. This method The boiler is blown down a cerof control, which removes solid matter from the boiler at the rate it is fed in by the feed water, maintains a substantially constant boiler concentration. This method, however, does not bring about a reduction in concentration for materially increased loads, nor does it permit an increase in concentration when the load is reduced which is desirable in order to secure the highest quality of steam and at the same time reduce boiler blow-down to a minimum with a consequent saving of heat. When the load is increased to a point that is too high for the constant concentration fixed by the method of blow-down control described above, the steam generated will tend to increase in moisture content.

It has become the practice to purify the steam leaving the boiler of entrained moisture or boiler water. This prevents the steam from carrying moisture or boiler water with its highly concentrated impurities into the steam pipe lines, superheaters, engines, turbines and other steam plant equipment.

. By the use of suchpurified steam of high quality, greater efliciency is secured, and clogging, erosion, and other similar troubles are avoided.

Usually a steam purifier is installed within the steam outlet drum of the boiler in place of the so-called dry or collecting pipe. The moisture and impurities dissolved or suspended therein, are separated from the steam which must pass through the purifier to reach the steam outlet connection. The impurity laden moisture, thus separated, is collected in a suitable lower part of the urifier housing from which it is conveyed y a pipe drain line to a steam trap or other discharge which is usually outside of the boiler. The steam trap accumulates the moisture, and each time it becomes filled with-the same, it efi'ectsa discharge.

A satisfactory steam purifier of this character is shown and described in the copending a plication of Walter J. Hughes and others,

erial No. 188,104, filed May 2nd,- 1927.

While in general a steam purifier collects and discharges to the trap more moisture as more steam is produced by the boiler, and lem moisture as less steam is produced by the boiler, it is apparent that the amount of water discharged by a steam purifier, and the rate of the discharge is a functionof other variables also. Thus, if the quality of the steam varies due to a greater or less turbulence in the boiler, which may be caused by a change in the steaming rate or of the concentration or of the boiler water level, more or less water will be collected and discharged by the purifier. In this manner the amount of the steam purifier discharge and the rate of the discharge will be an indication of the general conditions of operation instead of any single element.

The purifier discharge, therefore, is another means, besides the boilerfeed and steam output, of controlling the blow-down of the boiler. The control of the boiler blow down by the purifier discharge is advantageous since it regulates the condition of the boiler water by reducing the concentration of the boiler water for high loads and permitting increases in concentration for low loads. This method of blow-down control tends to compensate the boiler conditions to the quality of the steam generated.

In the preferred purifier discharge control, means are provided for blowing down the boiler a fixed amount each time the steam purifier trap makes a discharge. The amount of blow-down may be regulated by a valve or orifice to any desired amount; thus, if the trap makes a discharge for each gallon of accumulated moisture from the steam, the blow-down line actuated by the trap may contain a valve or orifice set to provide escapement of 3 gallons, or any other amount, from the boiler at the same time and with the same frequency. Since the water collected in the purifier is practically all actual boiler water the discharge of this water is in actuality a partial blow-down of boiler.

This steam purifier discharge is alone seldom sufficient to afford an adequate blowdown, but it must be taken into consideration as a part of the total boiler water removed. In the present example the total blow-down will be the combined discharge of the blowdown line and the steam trap which in this case is 4 gallons.

If the steam quality is say 99 percent, then the trap discharge represents a steam moisture content of 1 percent andthe trap actuated blow-down represents three times this amount, making a total of 4 percent of the steam output. Further if the steam quality lowers due to a too high boiler water concentration, say to 98 percent, then the trap will discharge twice as often. Simultaneously, the trap actuated blow-down will be doubled and in eflz'ect a total blow-down of 8 percent is reached. Whenever this occurs fresh boiler feed Water replaces the blowdown and so reduces the concentration that the reverse sequence takes place. Steam quality improves, less trap discharges take place, and there is proportionately less trap actuated blow-down. In this manner concentration of the boiler water is reduced automatically until boiler steaming conditions quiet down to the production of high quality steam with I which there is at the same time a reduced or desira le to combine the trap discharge andthe trap actuated blow-down causing them to pass together through a heat exchanger in which boiler feed water makes contact with the heating interchanging. elements. Separate heat interchangers can be placed upon the purifier discharge line and the blowdown line, and such heat interchangers could also be placed before the particular discharge means used, instead of after as shown.

The accompanying drawings show several embodiments of the invention.

In the drawings: Fig. 1 shows an arrangement by means of which the moisture collected in the steam purifier actuates an intermittent blow-down;

Fig. 2 shows a diagrammatical arrangement by means of which the moisture collected in the steam purifier actuates a continuous blow-down, and

Fig. 3 is across section taken along lines 33 of Figs. 1 and 2, and shows means for maintaining a substantially constant liquid level within the boiler which may be used in plonnection with the apparatus described erem.

In 'Fig. 1 boiler drum 11 is about half from whence it passes to asteam system.

The collected moisture and impurities pass out of the purifier casing into the continuously slanting. drain-pipe 16 to a steam trap 17 outside of the boiler.

The steam trap 17 contains a ball float 18 to which is attached-a rod 19, which moves a pivoted lug 20 having two fixed projecting pins 21. These fixed pins 21, when moved by the ball float 18, engage and move the trip weight 22 to either the left or the right, depending upon the level of the water in the chamber 17. Attached to the trip weight is the cam 23 which actuates abell crank lever 24. In the figure the trip weight is shown to the right depressing the horizontal arm of lever 24, which is its position when the collecting chamber is about to discharge or discharging. The bell crank lever 24, when in this position, will pull the rod 25 to the left, opening the pilot valve 26, which will 'cause the admission of steam under boiler pressure to the lines 27 and 28, whichwill result in a discharge from the steam trap 17 and from the water space 12 of the boiler in a manner which will be subsequently-de-- scribed. When the chamber 17 discharges and empties the ball float 18 will descenduntil the weight 22 passes the centerv position and falls to-the left. This will cause the cam 23 to release instantly the horizontal arm of the bell crank lever 24, which will move the valve rod 25 to the right and quickly close the pilot valve 26. When the trap 17 fills again the reverse operation will take place. The ball float,18 will ascend until the trip weight 22 is moved past the center posi- N tion by the pins 21, whereupon the trip weight will fall to the right again and will depress the horizontal arm of the bell crank lever 24, opening the pilot valve 26.

The steam under boiler pressure, admitted into lines 27 and 28 by the pilot valve 26, is conveyed to the cylinders of the valves 29 and 30, which open and close the boiler blowdown and steam trap discharge lines respectively. Since the areas of the pistons 31 and 32 are greater than the areas of the valves 33 and 34, when boiler pressure acts through the lines 27 and 28 against the pistons 31 and 32,\the unbalanced effect causes opening of V the valves 33 and 34 in a substantially in stantaneous manner, compressing the springs 35 and 36 and providing free passage from 39 to 40 on the boiler blow-down line and from .chamber of the steam trap 17 through the cage 42 to the discharge line 43. The mois ture collected in the chamber 17 is thus quickly discharged by boiler pressure, and the 'boiler is blown down simultaneously a defivalves 33 and 34 and the representation of the sizes of the pipes 40, 43 and 41 upon Fi 1 is purely diagrammatic. When the va ves 33 and 34 are open,-the water will be discharged therethrough to atmospheric pressure. At all times the pressure in lines 40, 43 and 41 will be. substantially atmospheric.

When the lowered level of water in the chamber 17 effects closure of the pilot valve 26 as described above, the steam underiboiler pressure will'be'cut off from the pistons 31 and 32. Leakage around the pistons 31 and 32, together with the action of the compressed springs 35 and 36, will result in very rapid closureof the valves 33 and 34. The bo1ler pressure in the lines 37 and 16 assists the springs 35 and 36 in closing the valves 33 and34.

It is desirable to have all valves described, of a type which open and close quickly, substantially as described herein, in order that wire-drawing which causes undue wear, may be avoided. Another desirable feature in the quick opening and closing of the valves, especiall those which discharge water from the puri er and from the boiler blow-down connection, lies in the, better proportionment of boiler blow-down to steam moisture content due to a more simultaneous action of the two.

The combined discharges from the boiler blow-down 40 and the steam purifier 43 are combined in the pipe 41 and flow through the closed type heat interchanger 44, where they give up their heat to the incoming feed water. They then flow to waste through the pipe 45. The feed water will enter the heat interchanger through pipe 46, and after hav-' ing ac uired the heat of the discharged water, wi 1 enter the Water space of the boiler through the pipe 47.

In case it is desired to directly operate the valve 29, such can be accomplished by closing the valve 48 and opening the valve 49, whereupon steam under boiler pressure will flow into the cylinder of the valve 29 from the upper part of the steam trap casing 17. In case it is desired to supplement or replace the boiler blow-down through the valve 29, such can be effected by operating the valves 50 and 51. The valve 50 will open the boiler blow-down line directly to waste.

In Fig. 2 the steam purifier discharge fiows down through the continuously sloping drain pipe system 16 into the steam trap 60. The steam trap contains the vertically sliding dome element 61, under which the water discharge or the combined steam and water discharge from the steam purifier will be introduced by means of the pipe 16. The water discharge so introduced will pass from under the dome element 61 through the openings 62 upwardly through the outer part of the steam trap casing 63, and then past the valve 64, into the discharge line 68; When steam is discharged into the trap by the pipe 16, or when a mixture of steam and water is discharged into the trap 60 by the pipe 16, the steam will collect in the upper part of the dome structure 65 and will slowly leak out through the pin-hole opening 66 in the top of the dome and condense. The buoying effect of the steam will cause the dome 61 to rise in the steam trap casing, and this will close thevalve 64 and prevent any further discharge from the steam trap. As the steam subsequently slowly leaks out through the pin-hole opening 66 and condenses, the dome '61 will again sink to the bottom of the steam trap casing, opening the valve 64 and again permitting discharge into the line 68. The dome 61 is uidedin its upward and downward motion in the steam trap casing by the projecting portions 67. The discharge from the line 68, which will be substantially constant under uniform operating conditions when the steam generated is of a constant quality, flows into the orifice box 69.

The water contained in this orifice box 69 will flow out through the adjustable or replaceable orifice 70 intothe discharge pipe 71. The discharge box 69 constitutes one side of a balance structure having the pivoted beam72, which has as the other side the orifice box 89 upon the boiler blow-down discharge line. The balance beam 72 is normally held in horizontal position through the vertical arm or rod 73, to which is attached the sliding weight 74 which can be set at any desired height thereon by the set screw 75. The stops 76 prevent the beam 72 from being tilted too far to the right or the left. 7

The movement of the balance causes the movement of the rod 79 through the link 78, which is attached to the balance structure by the pivot connection 77. The movement of the rod 79 operates a sliding valve in the pilot valve structure 80 so as to open a connection between the line 81, to which water is being supplied under pressure, and either the line 82 or 83, which will cause such water under pressure to be supplied to either the upper end or the lower end of the cylinder 84, causing a movement of the piston 85. This movement regulates the amount of opening of valve 86 which is upon the boiler blow-down line 87.

When larger quantities of water are discharged into the orifice box 69, the balance will tilt down to the left. This will actuate the pilot valve 80 in such a manner that the water under pressure from the line 81 passes into the line 83, raising the piston 85 and in turn further opening the valve 86. The water contained in the upper part of the cylinder 84 will be discharged to the line 82 through the pilot valve 80 to the line 88. This will permit an increase in the cdntinuous discharge through the valve 86 until the concentration of the boiler water has been reduced to such a degree that the steam quality returns to its normal value.

When less moisture-is discharged by the steam purifier, the balance structure will then tilt to the right with the result that the pilot valve 80 will be so operated, that water under pressure will be admitted from the line 81 to the line 82 and from thence into the upper part of the cylinder 84, causing downward movement of the piston 85. At the same time, the water contained in the lower part of the cylinder 84 will pass out through the pipe 83 through the pilot valve 80 to the line 88.

The apparatus should be so arranged, and

the orifices and90 should be so adjusted that when a steam of desired quality, say

98 percent, is generated and passed through the s'teampurifier, suflicient water will be 5 discharged through the lines 68 and 87 into the orifice boxes 69 and 89 respectively,'so that the balance structure will be in an equilibrium or balanced condition. When it is desired to supplement the boiler blow-down through the line 87, or when it is desired to replace the boiler blow-down through the valve 86, such can be done by operation of the valves 92 and 93. V

To illustrate the method of operation in Fig. 1 when the load is constant with substantially constant quality feed water and constant steam quality, a boiler having the following characteristics may be taken:

Constant feed of 6,000 gallons per hour, containing ten grains of solid per gallon.

S'team quality to be maintained-98 percent (that is, moisture content of steam-2 percent) -Constant solid content not to be exceeded- 250 grains per gallon.

Trap set to discharge every 2 gallons of separated moisture.

It the steam is considered to be produced as rapidly as the water is fed irg the trap will discharge once every minute. iuce approximately 100 gallons of water will be vaporized and removed as 98 percent steam every minute, 1,000 grains of solids will be fed in .during the same interval. Since the. discharge from the trap will only remove 500 grains of solids, it is desirable to blow-down the boiler simultaneously an amount of 2 gallons to make up the other 500 grains. This blow-down is controlled by the operation ofthe steam trap 17 and the boiler pressure, and can be varied by the adjusting valve 38.

If the loadon the boiler suddenly increases, the quality of the steam will decrease and its moisture content will increase. lhe solid content of 250 grains per gallon would be too high for the production of steam of.98 percent quality so that it is necessary to reduce :the solid content of the boiler water. If the quality of the steam decreases. to 96 percent,

due to such a load variation, twice. thequantity of water will be separated in the purifier and the total discharge of steam trap and blow-down will amount to 8 gallons per minute instead of 4, and an increased discharge will continue until the solid content of the boiler water had been reduced to such a value that 98 percent steam is produced.

U Such a decrease in the steam quality may also be caused by an increase .in the solid content of the feed water. In such a case the steam trap with its controlled blow-down .will be discharged more frequently with the result that the boiler water concentration will be maintained at such a value that the desired steam quality will be attained.

The operation of the arrangement shown in Fig. 2 is very similar in principle to the operation of the apparatus of Fig. 1. When it is desired to maintain a constant steam quality of 98 per cent, the orifices 70 and 90 can be set so as to continually discharge the desired amount of water. If the desired steam quality is 98 per cent and the feed and amount of steam evaporation is as is stated above the orifice 70 will be of such a size and shape as to discharge two gallons of moisture every minute under a predetermined head in the orifice box 69. If, at the same time, it is also necessary to discharge 2 gallons of water from the boiler blow-down, the orifice 90 will also be of such a size and shape as to obtain this desired amount of blow-.down. In any case, the orifices 70 and 90 and orifice chambers 69 and 89 are so proportioned that, when the steam of the desired quality is being produced by the boiler, the amount of water in orifice chambers 69 and 89 will substantially balance each other. A continuous blowdown of this character is very advantageous inasmuch as all changes in. boiler operating conditions take place almost imperceptibly.

A constant level may be maintained in the boilers shown and described in connection.

with each of the modifications disclosed heretofore by a device such as shown in Fig. 3, for example. As shown, this device may comprise a vertical pipe 200 integral with pipe 47 in the modification shown in Fig. 1,-

and with pipe 87 in the modification shown in Fig. 2. This vertical pipe connects through horizontal pipe 201 with the inlet 202. Liquid level v chamber 203 contains float 204 which actuates valve 205 in horizontal inlet pipe.

201 by means of levers 206, 207 and 208. When the liquid level within the boiler and chamber decreases the float is lowered, thereby operating to open the valve 205 to allow additional water toflow into the boiler to restore the normal level. If the level within the boiler exceeds a predetermined value the float is raised, thereby closing the valve 205.

To one skilled in the art, many variations of our invention will occur upon a reading of the purifier, a steam trap, means for conducting collected moisture from the steam purifier to the steam trap, a blow-down for the boiler actuated bv discharge of said trap and an adjusting means for regulating the amount purifier, a steam trap exterior to the boiler, a

, means for conducting collected moisture from said purifier to said trap and means actuated by said trap for periodically blowing down the boiler.

4. In a boiler control apparatus, a stea purifier, a steam trap, means for conducting collected moisture from said purifier to said trap, means actuated by said trap .for pcriodically blowing down the boiler, and heat interchanging means for the boiler feed water and the purifier discharge.

5. In a boiler control apparatus, a steam purifier, a steam trap, a means for conducting water collected in said purifier to said trap, means actuated by said trap for periodically blowing down the boiler, means for combining the trap discharge and the boiler blowdown and means for heat interchanging the combined discharge and the boiler feed water.

6. An apparatus for regulating the condition of boiler water, which comprises a steam purifier, means for discharging said steam purifier means actuated by the amount of the Water discharged from said purifier for removing suitable quantities of boiler water, and means for recovering the heat in such discharged water.

7 The method of regulating boiler conditions which comprises removing moisture from the steam produced, and regulating the amount of blow-down from the water space in proportion to the amount of water obtained from the steam.

8. An apparatus for regulating the quality of steam, which comprises means affected by the quantity of steam output from a boiler, means for discharging water from said boiler, means adapted to remove suitable quantities of boiler water by said discharging means, and cooperating means actuated by said first mentioned means adapted to operate said last mentioned means.

9. An apparatus for regulating the condition of boiler water which comprises a steam purifier, means for discharging said steam purifier, means for discharging the boiler, and means responsive to the amount of water discharged from said purifier for removing suitable quantities of boiler water by said boiler discharging means. 10. An apparatus for regulating the condition of boiler water comprising means responsive to the quality of the steam generated by said boiler, a blowdown line from said boiler, a valve upon said blowdown line, and means actuated from said first mentioned' means for actuating said valve.

11. An apparatus for regulating the quality of steam generated in a boiler, comprising means responsive to the quality and quantity of the steam generated by said boiler, a blowdown line from said boiler, a valve upon said blowdown line, and means actuated by said first mentioned means for actuating said valve.

' 12. A boiler control apparatus which comprises a means for separating the ,moisture in steam, a collecting chamber for said moisture, a blowdown line to said boiler, and means associated with the separated moisture in said collecting chamber adapted to open and close said blowdown line.

13. In a boiler control apparatus, a boiler shell containing a steam space in the upper portion thereof, a steam purifier in the steam space of said boiler shell, a means of admitting steam to said'purifier, a conduit for removing purified steam from said purifier and conveying it to the steam outlet of the boiler, a conduit for draining the impurities to without the boiler shell and a boiler blow-down means outside of the boiler actuated by said drainage.

1 14. In a boiler control apparatus, a boiler shell, a valved blowdown line from said boiler shell. and a means for maintaining the steam quality constant comprising a means for removing the moisture from the steam, a collecting chamber for the separated moisture, a float in such chamber, and a means actuated by said float adapted to discharge said chamber and to open and close the valve on the blow-down line.

15. In a boiler control apparatus, a boiler shell, a blowdown line from said boiler shell,

a piston operated valve upon said blowdown.

line and a means for maintaining the steam quality constant comprising a steam purifier in the steam space of said boiler shell, a float chamber Without said boiler shell, a drain line from said purifier to said float chamber, a pressure fluid line to said above mentioned piston operated valve, and a valve upon said fluid pressure line actuated by the movement of the float, in said float chamber.

16. In a boiler control apparatus, a boiler shell, a blowdown line from said boiler shell, a piston operated valve upon said blowdown line, and a means for maintaining the steam quality constant comprising a steam purifier in the steam space of said boiler shell, a float chamber without said boiler shell, a drain line from said purifier to said float chamber, a discharge line from said float chamber, a piston operated valve upon said discharge line, a pressure fluid line to said above mentioned piston operated valves, and a valve upon said fluid pressure line actuated by the movement of the float in said float chamber.

17. In an apparatus for regulating the quality of steam, means responsive to the steam purifier in the boiler shell'through which the steam from said boiler must pass, a chamber adapted to collect the separated moisture from said purifier, means to discharge said chamber, and means actuated in coordination with said last named means to remove suitable quantities of boiler water.

18. An apparatus for producing steam of constant quality comprising a boiler, a steam purifier, a means of discharging said purifier, a chamber for receiving said discharge, means for discharging said chamber, and means associated with said last mentioned means for blowing down the boiler.

19. The method of regulating boiler conditions which comprises appraising both the quantity and quality of the steam generated by the boiler by separating the moisture therefrom, and controlling the quality of the steam by blowing down the boiler in proportionto the moisture separated.

20. The method of regulating boiler 'conditions which comprises separating the moisture from the steam generated by the boiler, and maintaining a constant quality steam by utilizing a higher boiler concentration when smaller amounts of moisture than normal are being separated per unit time.

21. In a boiler controlling apparatus, a steam purifier, a steam trap, means for conducting collected moisture from the steam purifier to the steam trap, a blowdown for the boiler, and means in association with the discharge of said trap for actuating said blowdown.

22. In the operation of a boiler, the process which comprises passing steam generated by the boiler through a purifier separating the water from said purifier, and regulating the boiler blowdown in accordance with the amount of water separated from said purifier.

In testimony whereof we have hereunto subscribed our names.

WALTER J. HUGHES.

WALTER H. GREEN. 

